One pot synthesis of new benzopyranopyridines via Friedlander condensation

A facile, green synthetic route to new benzopyrano [2,3-b] pyridines in excellent yield via Friedlander condensation has been developed by the reaction of 2-amino-3-formylchromone 1a–b and cyclic active methylene compounds 2a–e in the presence of Zn(l-proline)2 as an efficient, stable, and inexpensive Lewis acid catalyst in water. The present methodology offers several advantages such as shorter reaction time, mild reaction conditions, simple operational procedure, recyclable catalyst, and safe to the environment.